With an increase in capacity of information processing in recent years, various information recording technologies have been developed. In particular, the surface recording density of an HDD (a hard disk device) using magnetic recording technology is continuously increasing at an annual rate of approximately 50%. In recent years, an information recording capacity exceeding 500 gigabytes per disk has been desired for a magnetic disk with a 2.5-inch diameter for use in an HDD or the like. To fulfill such demands, an information recording density exceeding 700 gigabits per square inch is desired to be achieved.
Also in recent years, to further improve recording density, a perpendicular magnetic recording type is adopted for magnetizing a recording layer in a direction perpendicular to a magnetic disk plane. Under these circumstances, to further increase recording density of the magnetic disk, linear recording density (BPI: Bit Per Inch) in a circumferential direction and track recording density (TPI: Track Per Inch) in a diameter direction have to be both improved, while a predetermined S/N ration is ensured.
As a method of improving track recording density, there is a method of decreasing a track width by narrowing a recording head. However, when the recording head is narrowed, recording magnetic field density is decreased, thereby posing a problem such that a sufficient S/N ratio cannot be ensured. To get around this, as a method of solving this problem, a type (a shingle recording type) is suggested in which information is written in a partially overlapping manner in adjacent tracks (for example, refer to Patent Document 1 and Patent Document 2). By applying the shingle recording type, the recording head can be made large, thereby advantageously ensuring recording magnetic field density and ensuring an S/N ratio and also allowing achievement of a track narrower than a recording width actually written by an actual recording head.